Loans - Consumer Loans by Risk Rating Categories (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	$ 13,273,392	$ 12,990,779
Originated
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	7,959,769	7,458,401
Originated | Residential mortgage
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	1,594,376	1,475,342
Originated | Consumer installment
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	1,342,063	1,282,588
Originated | Home equity
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	591,441	595,422
Acquired
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	5,313,623	5,532,378
Consumer loan portfolio
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	5,468,202	5,396,567
Consumer loan portfolio | Residential mortgage
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	3,133,465	3,086,474
Consumer loan portfolio | Consumer installment
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	1,481,057	1,433,884
Consumer loan portfolio | Home equity
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	853,680	876,209
Consumer loan portfolio | Originated
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	3,527,880	3,353,352
Consumer loan portfolio | Originated | Residential mortgage
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	1,594,376	1,475,342
Consumer loan portfolio | Originated | Consumer installment
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	1,342,063	1,282,588
Consumer loan portfolio | Originated | Home equity
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	591,441	595,422
Consumer loan portfolio | Originated | Performing
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	3,517,663	3,342,153
Consumer loan portfolio | Originated | Performing | Residential mortgage
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	1,587,627	1,468,373
Consumer loan portfolio | Originated | Performing | Consumer installment
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	1,341,308	1,281,709
Consumer loan portfolio | Originated | Performing | Home equity
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	588,728	592,071
Consumer loan portfolio | Originated | Nonperforming
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	10,217	11,199
Consumer loan portfolio | Originated | Nonperforming | Residential mortgage
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	6,749	6,969
Consumer loan portfolio | Originated | Nonperforming | Consumer installment
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	755	879
Consumer loan portfolio | Originated | Nonperforming | Home equity
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	2,713	3,351
Consumer loan portfolio | Acquired
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	1,940,322	2,043,215
Consumer loan portfolio | Acquired | Residential mortgage
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	1,539,089	1,611,132
Consumer loan portfolio | Acquired | Consumer installment
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	138,994	151,296
Consumer loan portfolio | Acquired | Home equity
Recorded investment of loans in consumer loan portfolio based on credit risk profile of loans in performing and nonperforming status
Total loans	$ 262,239	$ 280,787